this is boggling my mind... some experimenting has shown some oddities about my intel dp35dp:
- it has two different fan control circuits. out of 4 fan connections, two are 4 pin and pwm controlled, and two are 3 pin non pwm. but the non pwm is also controlled:
- the non pwm circuit is a real kludge job. it has 2 settings- 5v and 12v. what makes it a kludge is that under normal booting temps it gets stuck between and the fans are constantly changing speeds at about a 1hz frequency... the fans don't seem to like it as they make a weird buzzing noise in addition to the speed change sound. very annoying.
-my multimeter tells me it seem to be changing it by way of the ground since fan+ to ground (on a molex connector) is a constant 12v, but fan+ to fan- gets the 1hz 5 to 12v fluctuation.
-I checked, it is not the psu putting out that much ripple.
-they were also kind enough to not include any tachometer sence that lm sensors under linux can detect... all lm sensors can detect is the cpu's temp sensor.
sounds like to only way to get rid of the fan noise is to find a pwm 90mm fan for the back... the cpu cooler is already pwm.
- it has two different fan control circuits. out of 4 fan connections, two are 4 pin and pwm controlled, and two are 3 pin non pwm. but the non pwm is also controlled:
- the non pwm circuit is a real kludge job. it has 2 settings- 5v and 12v. what makes it a kludge is that under normal booting temps it gets stuck between and the fans are constantly changing speeds at about a 1hz frequency... the fans don't seem to like it as they make a weird buzzing noise in addition to the speed change sound. very annoying.
-my multimeter tells me it seem to be changing it by way of the ground since fan+ to ground (on a molex connector) is a constant 12v, but fan+ to fan- gets the 1hz 5 to 12v fluctuation.
-I checked, it is not the psu putting out that much ripple.
-they were also kind enough to not include any tachometer sence that lm sensors under linux can detect... all lm sensors can detect is the cpu's temp sensor.
sounds like to only way to get rid of the fan noise is to find a pwm 90mm fan for the back... the cpu cooler is already pwm.
Comment